star wars - Can a ship in hyperspace see other ships?

The evidence in the films suggests that no, they can't see each other, but they can detect each other by other means.

We see what light speed looks like several times when the Falcon makes the jump: a ring of lights streaking past. This effect is constant throughout the series regardless of location and does not appear to allow light speed travelers to visually discern local space in anyway. Contrast this with, for example, Star Trek, where individual stars can be seen streaking by.

While there is no technology in our universe that would allow the ships to detect each other, clearly a universe that permits matter to move faster than light would allow energy to do so as well. The manner in which a ship's computer calculates a light speed jump suggests that it is scanning the path ahead much faster than the speed of light to make sure the path is clear. (The only other explanation is that every ship contains a complete and perfectly accurate model of at least the Galaxy, which is problematic enough before the empire starts blowing up planets and really throwing things off.)

However, this scanning technology does appear to be highly directional based on how easily one ship may elude another by jumping to light speed. Without knowing the exact direction to scan in, the pursuing ship seems to have no way of locating the ship that escaped it (which is pretty much always the Falcon). So it is probably possible for one ship to covertly stalk another at light speed and remain undetected (much like one submarine following another), but in the scenario you mention where the ships are aware of each other, they should be able to detect each other just fine. The computers would display the ships visually to the crew so they could be "seen" in this manner.